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Solutions

Solutions. Solution – homogeneous mixture in which solute & solvent particles are evenly distributed in one another solvent – the dissolving medium; thing that does the dissolving solute –the dissolved particles; thing that is dissolved

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Solutions

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  1. Solutions

  2. Solution – homogeneous mixture in which solute & solvent particles are evenly distributed in one another • solvent – the dissolving medium; thing that does the dissolving • solute –the dissolved particles; thing that is dissolved • solutes and solvents can be solids, liquids, or gases

  3. Solubility – amount of solute that dissolves in a quantity of solvent at certain temperature and pressure Solutions can be: a) unsaturated – contains less solute than solvent can possibly dissolve b) saturated – contains as much solute as can be dissolved by solvent

  4. c) supersaturated – contains more solute than can normally be dissolved by solvent; not very stable – slight disturbance to solution will cause solute to precipitate or crystallize

  5. Terms related to solubility • soluble– substance that will dissolve in a solvent • insoluble – substance that will not dissolve in a solvent • miscible – when 2 liquids will dissolve in each other in any proportion (ex: water and ethanol) • immiscible – when 2 liquids are insoluble(ex: water and oil)

  6. Electrolytes • excellent conductors in liquid state or dissolved in water (aqueous) • In order for a solution to carry an electrical current, it must contain ions that are free to move. • Acids, bases and ionic compounds all ionize (break into ions) in water to form free ions. http://www.schooltube.com/video/36d820507a4c220061eb/The-Basics-on-Electrolytes

  7. Factors Affecting Solubility • agitation of the system – increases collisions between solute and solvent particles • particle size – smaller dissolves faster because more surface area • temperature – solutes generally dissolve faster at higher temps. – higher kinetic energy at higher temps. – stronger and more frequent collisions between solute and solvent particles - Exception: solubility of gases inversely proportional to temperature

  8. Concentration of Solutions • Molarity – M – mols of solute per L of solution • Example: 5 M – dissolve 5 mol of solute in enough solvent to make 1 L of solution

  9. Calculating molarity (M) • convert mass of solute (g) to mol using molar mass • convert volume of solution to L • use formula: M =molssolute literssolution

  10. Example 1 • What is the molarity of 2.3 moles of sodium chloride in 0.45 liters of solution? M=molssolute literssolution M = 2.3 mol = 5.1 M 0.45 L

  11. Example 2 What is molarity of a solution prepared by dissolving 37.94 g of KOH in H2O, then diluting the volume to 500 mL? mass = 37.94 g KOH 1 mol KOH = 0.676mol 56.11 g KOH molar mass KOH volume = 500 mL 1 L = 0.500 L 1000 mL molarity = 0.676 mol = 1.35 M 0.500 L

  12. Dilutions • stock solution – mixture w/ high concentration of solute; can be diluted by adding additional solvent to get molarity needed • use this equation to solve for unknown: M1· V1 = M2· V2

  13. Example What is the molarity of a solution that is made by diluting 50.0 mL of 4.74 M solution of HCl to 250.0 mL? • M1 = 4.74 M • V1 = 50.0 mL • M2 = ? • V2 = 250.0 mL M1V1 = M2V2 • M2 = 0.948 M

  14. “Like dissolves like” Rule • Polar solvents dissolve ionic and polar solutes • partial positive & negative charges of polar molecules are attractive to one another • Due to an uneven sharing of electrons in a molecule • polar solvents with partial + and – charges are attracted to + and – ions in ionic compounds • Nonpolar solvents dissolve nonpolar solutes http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

  15. The Uniqueness of Water! • Structure of H2O • Lewis Dot Structure • VSEPR Shape • Electronegativity (H=2.1 and O=3.5) • Hydrogen bonding

  16. Physical Properties of Water • Density of Ice • Universal Solvent • High melting and boiling points • Cohesion (surface tension) • Adhesion (capillary action) • High specific heat (ability to hold heat) ALL OF THESE ARE DUE TO THE STUCTURE OF WATER (polar and hydrogen bonds)!!!

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